This invention relates to a liquid atomizer in which electrical oscillation applied to piezoelectric elements is converted into mechanical vibration, and a variety of liquids such as liquid fuels are atomized by utilizing the mechanical vibration.
Various devices have heretofore been proposed to atomize liquid using vibration of piezoelectric elements. In the field of fuel injection devices for internal combustion engines, for instance, liquid fuel is injected onto a vibrator of a hollow cylindrical member that is vibrated by a piezoelectric element. The fuel is atomized by the ultrasonic vibration of the vibrator in order to promote the atomization of fuel injected from a fuel injection valve, as is disclosed in Japanese Pat. Publication No. 11224/1985 and U.S. Pat. No. 4,563,993.
Piezoelectric elements used for liquid atomizers of this type deform to cause displacement therein when a voltage is applied thereto. The displacement, however, is as small as about 0.1 micron when a voltage of 100 volts is applied. Where only a pair of piezoelectric elements only are used as in the above-mentioned prior art, therefore, it is not possible to obtain a sufficiently large vibration. It has therefore been attempted to apply a large voltage (usually 200 volts or higher) to the piezoelectric elements or to provide the piezoelectric element with a mechanical vibration amplifying means such as a horn to amplify the mechanical vibration, thereby to take out mechanical vibration of a desired amplitude and to transmit the thus amplified mechanical vibration to the vibrator.
To atomize liquid using a vibrator of a hollow cylindrical member, a sufficient amount of displacement is imparted to the hollow cylindrical member. To obtain the displacement of such a degree, so far, a voltage of about 200 volts has been applied to the piezoelectric elements and the displacement has been amplified by a tapered horn.
According to the conventional liquid atomizer which makes use of the piezoelectric element as described above, a relatively large voltage is applied to the piezoelectric element and a mechanical vibration amplifying means such as a horn is used to amplify the displacement that is to be transmitted to the vibrator. For this purpose, means for increasing the voltage must be incorporated in the circuit which drives the piezoelectric element and a member such as a horn must be used, resulting in an increase in the manufacturing cost and in the size of the whole device.